(a) Field of the Invention
The present invention relates to a fuel injection device of the type adapted to measure fuel by the opening time and opening area of a gate disposed in a fuel feed passage. Particularly, it relates to improvements in the fuel injector.
(b) Description of the Prior Art
A known fuel injection device, as shown in FIG. 1, comprises a body 1 and a rotor 2 disposed in the body 1. The body 1 is provided with a fuel feed port 3, fuel distributing ports 4 equidistantly spaced in accordance with the number of cylinders of the engine, and measuring ports 5 communicating with said distributing ports 4. The rotor 2 is provided with a fuel inlet port 6 communicating with the fuel feed port 3 at all times, and a single fuel measuring port 8 communicating with said fuel inlet port 6 and associated with the measuring port 5 in the body. The measuring ports 5 and 8 in the body and rotor are a combination of windows substantially in the form of a triangle with one side circumferentially extending, and an orifice or a combination of windows substantially in the form of a rectangle with two sides extending circumferentially, and a slit, and they constitute a gate. The rotor 2 is driven for rotation in synchronism with the engine rpm and has its axial position controlled in accordance with the amount of air being sucked into the engine. As a result, the opening time of the gate 5, 8 is controlled in connection with the engine rpm and the amount of suction air. The fuel from a tank 9 is pressurized by a pump 10 and controlled to a constant pressure and it is fed to the fuel feed port 3. The fuel measured by the gate 5, 8 is distributed from the fuel distributing ports 4 and is injected into the suction pipe by an automatic valve type fuel injector 12. The injector 12 comprises an injection valve 14, a valve seat 15 and a valve opening pressure determining valve spring 16, which are disposed in a body 13.
In the fuel injection device of the type described above, the rise in the pressure of delivered fuel, particularly in the high speed range, is so sharp as to open the injection valve 14 too wide, causing a problem that an excessive amount of fuel is injected. FIG. 2 is a graph showing the delivery pressure of fuel measured at the distributing ports 4, it being seen that in the low speed range since the communication of the gate 5, 8 is gentle, the rise in the pressure is relatively gentle as shown at a, while in the high speed renge the pressure rises sharply as shown at b. On the other hand, since this pressure is applied directly to the injection valve 14, the latter will be opened suddenly. At this moment, the injection valve 14 which opens to the suction pipe is directly connected to the fuel tank 9 through the gate 5, 8, and the increase of the stroke of the injection valve 14, i.e., the increase of the degree of opening thereof will lead to the increase of the amount of injection.
Further, since the conventional fuel injector is of the type in which after the valve parts, i.e., the valve, the valve seat and the adjusting spring for adjusting the valve opening pressure have been assembled as a unit and adjusted, the injector is installed in the body, it has been impossible to finely adjust or alter the valve opening pressure. Further, since different valve opening pressures for the fuel injector are required for different fuel injection devices, exclusive injectors are required, which is irrational from the standpoint of manufacture.